chanani opened a new pull request, #4049:
URL: https://github.com/apache/logging-log4j2/pull/4049
## Summary
The `loadClass` method in `ThrowableExtendedStackTraceRenderer` only catches
`Exception`,
but `ClassLoader` can throw `NoClassDefFoundError`, which extends
`LinkageError` (an `Error`
subclass). This causes the entire log event to fail with
`AppenderLoggingException` instead
of gracefully degrading when a class in the stack trace cannot be resolved.
## Changes
- **`ThrowableExtendedStackTraceRenderer.java`**: Changed `catch
(Exception)` to
`catch (Exception | LinkageError)` in the `loadClass` method
- **`ThrowableExtendedStackTraceRendererTest.java`**: Added two test cases:
- Verifies rendering succeeds when a stack trace references a non-existent
class
- Verifies rendering succeeds when a custom `ClassLoader` throws
`NoClassDefFoundError`
- **Changelog entry**: Added
`4028_fix_catch_LinkageError_in_ThrowableExtendedStackTraceRenderer.xml`
## Root Cause
```java
// Before: Only catches Exception — NoClassDefFoundError (Error) escapes
catch (final Exception ignored)
// After: Also catches LinkageError, which is the parent of
NoClassDefFoundError
catch (final Exception | LinkageError ignored)
```
Java's `Throwable` hierarchy:
```
Throwable
├── Exception ← previously caught
└── Error
└── LinkageError ← now also caught
└── NoClassDefFoundError
```
Fixes #4028
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